Seismic surveying is used for identifying subterranean elements, such as hydrocarbon reservoirs, fresh water aquifers, gas injection reservoirs, and so forth. In performing seismic surveying, seismic sources are placed at various locations above an earth surface or sea floor, with the seismic sources activated to generate seismic waves directed into the subterranean structure. Examples of seismic sources include explosives, air guns, or other sources that generate seismic waves. In a marine seismic surveying operation, the seismic sources can be towed through water.
The seismic waves generated by a seismic source travel into the subterranean structure, with a portion of the seismic waves reflected back to the surface for receipt by seismic sensors (e.g., geophones, hydrophones, etc.). These seismic sensors produce signals that represent detected seismic waves. Signals from seismic sensors are processed to yield information about the content and characteristic of the subterranean structure.
For land-based seismic data acquisition, seismic sensors are implanted into the earth. Typically, seismic signals traveling in the vertical direction are of interest in characterizing elements of a subterranean structure. Since a land-based seismic data acquisition arrangement typically includes a relatively large number of seismic sensors, it is usually impractical to attempt to implant seismic sensors in a perfectly vertical orientation.
If a seismic sensor, such as a geophone, is tilted from the vertical orientation, then a vertical seismic signal (also referred to as a “compression wave” or “P wave”) would be recorded with attenuated amplitude. Moreover, seismic signals in horizontal orientations (also referred to as “shear waves” or “S waves”) will leak into the compression wave, where the leakage of the seismic signals into the compression wave is considered noise. Since the tilts of the seismic sensors in the land-based seismic data acquisition arrangement are unknown and can differ randomly, the noise will be incoherent from seismic sensor to seismic sensor, which makes it difficult to correct for the noise by performing filtering.